Not enough water pressure for MegaFlow?

[tallg]

If more than one cold tap is opened in our house the cold water pressure/flow drops considerably. This is a problem when someone is using the shower and a cold tap is run or the toilet flushed, as the shower goes scolding hot.

The hot water is fed from a Megaflow.

We have had a couple of plumbers round to assess the problem. Both measured the mains flow and pressure, with one concluding that the pressure wasn't sufficient to have Megaflow fitted and recommended we remove it altogether and replace it with something else, while the other said that the pressure was adequate and increasing the income pipe from 15mm to 22mm would solve the issue.

So I guess my question is what pressure and flow is required for a Megaflow, and will achieving these solve the issue with the cold water?

 

[crockett]

Around 20 l/min should suffice, and from 2 - 3 bar pressure too. Increasing the size of the mains to the megaflo would help too.

 

[spin99]

Search accumulator on this forum. I have one on a mains cylinder and find it works for me.

Sorry I never read your post properly, You need to know your pressure first, an accumulator will give you plenty of flow but if the pressure is to low it won’t help.

 

[tallg]

Around 20 l/min should suffice, and from 2 - 3 bar pressure too. Increasing the size of the mains to the megaflo would help too.

Thanks.

Out of interest, can you explain what effect increasing the pipe size will have and why that will help?

 

[Agile]

You need a flow rate of about 22 li/min with a pressure of about 1.5 Bar remaining in the mains supply pipes in the house.

Read about the difference between flow and pressure. Many people calling themselves plumbers dont seem to understand the terms.

 

[tallg]

Thanks. I think I understand the difference between flow and pressure, but if one or both is insufficient for a mega flow (ie below the figures you started) how will increasing the pipe size help? Will that increase both flow and pressure?

 

[onlyfitidealboilers]

just the flow.

 

[Agile]

Thanks. I think I understand the difference between flow and pressure, but if one or both is insufficient for a mega flow (ie below the figures you started) how will increasing the pipe size help? Will that increase both flow and pressure?

You may think that you understand the difference.

But by then asking how increasing the pipe size will help you demonstrate that will not!

The pressure is set by the water supplier so how do you think anything you do with a pipe will affect it?

Try reading the FAQ on this site for a start and then searching the web.

Tony

 

[tallg]

That was the point of my question. Perhaps I didn't word it well. I want to know how increasing the pipe size will help with my issue, as I don't see how it will solve the pressure problem, only increase the flow rate. I don't think it's unreasonable to ask someone why the solution they suggested will help.


Apologies if my knowledge is not up to your level. I thought that was the point of these forums - somewhere to come for help from people who know more than I do.

 

[simond]

There are two things missing from your post; the actual static pressure and flow measurements.

Without these, it is just pointless. Anyone quoting for an unvented should arrive with a Weir Gauge, and a pressure gauge. What were their readings?

 

[Agile]

Increasing the pipe size will increase the flow rate.

If you want to understand pressure and flow which you dont then you will need to learn about them. If it makes you feel better, about 60% of plumbers dont either!

Tony

 

[tallg]

There are two things missing from your post; the actual static pressure and flow measurements.

Without these, it is just pointless. Anyone quoting for an unvented should arrive with a Weir Gauge, and a pressure gauge. What were their readings?

Agreed. That's why I want to know what flow & pressure is required for a mega flow, so I can check against the readings the plumbers have taken (which I don't have at the moment)

 

[Agile]

You need a flow rate of about 22 li/min with a pressure of about 1.5 Bar remaining in the mains supply pipes in the house.

But as your plumbers dont understand pressure and flow they measure them seperately which does not do the same thing.

Tony

 

[tallg]

You need a flow rate of about 22 li/min with a pressure of about 1.5 Bar remaining in the mains supply pipes in the house.

But as your plumbers dont understand pressure and flow they measure them seperately which does not do the same thing.

Tony

Ok. I don't know how they measured them and didn't think I'd previously mentioned on here anything about how they took them. But I'll be sure to pass on your opinion of them.

 

[xr4x4]

Why don't you buy a £7 gauge and check the pressure yourself?

Is your stop cock in the road working and fully open, also the same to your house stop cock?